Recently, concerns about the environmental pollution and depletion of natural resources have been increased, so a solar cell is spotlighted as an alternative energy source having high energy efficiency without the problem of environmental pollution. The solar cell is classified into a silicon semiconductor solar cell, a compound semiconductor solar cell, and a stack-type solar cell depending on the composition of the solar cell. A solar cell including a CIGS light absorbing layer according to the embodiment may belong to the compound semiconductor solar cell.
The CIGS, which is a group I-III-VI compound semiconductor, has a direct transition energy bandgap of 1 eV or more as well as the highest light absorbing coefficient among the semiconductors. The CIGS has very stable electro-optic characteristics, so the CIGS is an ideal material for a light absorbing layer of the solar cell.
The solar cell is manufactured by sequentially depositing a substrate, a back electrode layer, a light absorbing layer, a buffer layer and a front electrode layer. In addition, the solar cell has a first through hole for shorting the back electrode layer, a second through hole for shorting the light absorbing layer and the buffer layer, a third through hole for shorting the front electrode layer and a fourth through hole for shorting an edge part.
The fourth through hole for shorting the edge part can be formed by a laser etching or by performing a mechanical etching using a needle after performing the laser etching.
However, in the case of the laser etching, the front electrode layer may be melted due to high energy of laser, so the front electrode layer may come into contact with the back electrode layer, thereby causing the short. In addition, the process step may be added in the two-step process, so the process efficiency may be lowered.
Therefore, it is necessary to provide a solar cell having a novel structure, in which the fourth through hole can be more efficiently formed.